Targeted gene disruption by use of a group 11 intron （targetron） vector in Clostridium acetobutylicum

Dear Editor： Clostridium acetobutylicum, a gram-positive, anaerobic, spore-forming bacterium, is capable of using a wide variety of carbon sources to produce acetone, butanol and ethanol. To improve solvent productivity of C. acetobutylicum, metabolic engineering is considered as a useful tool in developing strains with industrially desirable character-istics. However, to date, there are few useful methods for genetic manipulation of C. acetobutylicum, especially for gene disruption. To our knowledge, two types of vectors, including non-replicative and replicative integrative plasmids, have been developed for gene-inactivation in C. acetobutylicum. By using non-replicative integrative plasmids, buk and solR genes of C. acetobutylicum were inactivated [1,2]. However, due to their low frequencies of transformation and recombination, the non-replicative integrative plasmids are usually transformed at less than 1 integrative transformant per mg plasmid DNA. To obtain the integrative mutant, it may require higher transformation frequencies up to 10^5, but the typical transformation fre-quencies were reported at 10^3 [3].

Preparation and Characterisation of Collagen from Freshwater Fish Scales

Acid-soluble collagen (ASC) and pepsin-solubilized collagen (PSC) were prepared from the waste freshwater carp fish scales. The results of SDS-PAGE showed that purified collagens were composed of at least two different chains which were in accordance with the type I collagen with α chain composition of (α1)2α2. Compared with the carp fish ordinary muscle type I collagen , porcine dermis type I collagen and other seawater fish collagens, freshwater carp fish scales collagen contained relative high half-cystine (Cys-s), but lower denaturation temperature(Td) than the porcine dermis type I collagen. These collagens had evident absorption at 230 nm by UV-Vis spectra. The spectrum X-ray diffraction showed that the collagen remained single-helix and tri-helix configuration with the minimum values of the repeat spacings (d) of about 4.48 ? and 11.87 ?. Therefore, to make more effective use of limited-resources, carp fish scales can be a potential resource for the extraction of type I collagen or gelatin.

Modulating effects of RAMPs on signaling profiles of the glucagon receptor family

Receptor activity-modulating proteins(RAMPs)are accessory molecules that form complexes with specific G protein-coupled receptors(GPCRs)and modulate their functions.It is established that RAMP interacts with the glucagon receptor family of GPCRs but the underlying mechanism is poorly understood.In this study,we used a bioluminescence resonance energy transfer(BRET)approach to comprehensively investigate such interactions.In conjunction with c AMP accumulation,Gaqactivation andβ-arrestin1/2 recruitment assays,we not only verified the GPCR-RAMP pairs previously reported,but also identified new patterns of GPCR-RAMP interaction.While RAMP1 was able to modify the three signaling events elicited by both glucagon receptor(GCGR)and glucagon-like peptide-1 receptor(GLP-1 R),and RAMP2 mainly affectedβ-arrestin1/2 recruitment by GCGR,GLP-1 R and glucagon-like peptide-2 receptor,RAMP3 showed a widespread negative impact on all the family members except for growth hormone-releasing hormone receptor covering the three pathways.Our results suggest that RAMP modulates both G protein dependent and independent signal transduction among the glucagon receptor family members in a receptor-specific manner.Mapping such interactions provides new insights into the role of RAMP in ligand recognition and receptor activation.